An Approach Towards Low Energy Loss by End-capped Modification of A2–D–A1–D–A2-type Molecules for Tuning the Photovoltaic Properties of Organic Solar Cells

In this project, the study is focused on the substitution at determined sites of reference molecule (R) to enhance optoelectronic properties, which might affect the photovoltaic performance of organic solar cells. Herein, seven new molecules (M1 to M7) were designed by the modification of the terminal acceptors. The density functional theory was employed to explore optoelectronic properties. Majority of the molecules own exceptional optical properties than reference molecule, for instance, narrow bandgap, low excitation energy, lower binding energies, better oscillator strength and progressive light harvesting efficiency. The density of state, frontier molecular orbitals and transition density matrix diagrams indicated that the charge density transfer occurs from donor to acceptor. Moreover, charge transfer investigations of designed molecules with PTB7-Th complex were performed by analyzing the concentration of charge transfer over molecular orbitals, i.e., highest occupied to lowest unoccupied molecular orbitals. Thus, these computed molecules may be employed to develop efficient organic solar cell devices with promising photovoltaic prospects in the near future.